Hydraulic piston pumps are hydro-mechanical devices that are used in a variety of applications to pressurize fluid for various uses. One particular application is in cryogenic pumps that pump liquefied natural gas (“LNG”) to be combusted in an internal combustion engine. Recently, manufacturers of many mobile and stationary machines have occasionally configured those machines to combust alternative fuels such as LNG that may provide cost and/or environmental benefits over more traditional fossil fuel sources. Some cryogenic pumps are designed as structures that include a pump assembly at one end configured to be disposed in a cryogenic tank that maintains the fuel at cryogenic temperatures and a drive assembly at the other end which is disposed outside the tank and that is hydraulically activated to drive pumping elements in the pump assembly. The drive assembly may be configured as a piston drive having one or more reciprocating pistons supported in bores disposed in a piston housing. Various hydraulic configurations can be used to cause the pistons to reciprocate, which provides reciprocating motion that can be transmitted to the pump assembly to drive corresponding pumping elements disposed therein.
Cryogenic fuels may be stored under pressure and therefore the cryogenic pump may need to generate larger pressures to pressurize and direct the fuel from the storage tank to the engine. Because of the high pressures involved, the dimensions of the parts and clearances between parts may be critical and may need to be kept within close tolerances to prevent leakage while allowing relative motion of the parts, thereby requiring precision manufacturing of these parts. In addition, relative motion may cause the movable parts of cryogenic pump to wear overtime due to friction. It may become necessary to occasionally repair or overhaul the cryogenic pump for continued performance, which may be complicated by the need for close tolerances and precision machining. The present disclosure is directed to a particular configuration of a piston pump that may be suitable for use as the drive assembly in a cryogenic pump and that is adapted to facilitate and simplify manufacturing and maintenance.